I'm a dedicated double paddler. I'm a big believer in using what works for you. Some here use them very successfully, others have tried them and hated them. From what I can tell, it seems like the more experienced paddlers who are lucky enough to get out a lot, find them unwieldy after a traditional paddle. I'm sure a dedicated kayak er would feel the same with a canoe paddle. Your using a different set of muscles than with single paddle, but if your in moderate shape I don't think it's a problem.
For me, they really shine when your heading into a stiff wind or have one at your back. You can really fly then. I take a traditional paddle for trolling  while fishing or when conditions warrant using a J-Stroke to keep on course.
I needed a longer double paddle than a true solo, because I paddle a rented  SR16 tandem backward from the bow. My double paddle is 9 ft which with a " rolling" cruising stroke eliminates it banging on the gunnel's.

I'd try a double first and even if you like it, I'd buy a cheaper one until you see how it works for you on a trip with daily use.
My paddle is air-craft aluminum shaft/ Plastic paddle. Not the lightest, but stiff and strong and I don't have to baby it, like you might with a high end carbon fiber one. I even use it as a walking stick thru muddy portage holes, and in 2 pieces, I used it as fly poles with my Dry-Fly.
I payed $50 for it from Mohawk Canoes and it has more than met my expectations.